The present invention generally relates to a screening device implemented for the water supply of an industrial installation of some kind, in particular for the supply of cooling water for such an installation. More particularly it concerns a screening installation for reducing the detritus content of a water course downstream of said screening device in the proportion of the screened flow relative to the total flow of the water course concerned.
The invention finds a general application in the fields in which it is desired to remove at least part of the debris of various origins (vegetable, animal or human) that encumber and congest water courses, in order for the water downstream to be cleaner.
This is the case of certain water courses for reasons of appearance (rivers, urban canals, etc.).
It is also the case when the concentration of debris is too high for the use of the water downstream (intake of water for power stations, under-sized screening stations, etc.).
In practice, the filter member of the screening device is movable in an endless loop, which may be circular or elongate. The screening device is then a rotary drum or a band screen.
Solutions to the problem of reducing the detritus content of a water course downstream of a screening device are already known.
A first known solution consists of constructing a conventional water takeoff in a work of civil engineering with a gravity-feed inlet, treatment of the water by a conventional system comprising trash raking and screening, then pumping in order to return the water to the water course downstream.
Such a solution is however not satisfactory due to the cost of implementation of the work of civil engineering, which is in particular established beneath the water level.
A second solution consists in installing a filter in a casing with the screened stream created by mechanical extractors with a very small added manometric head. For the pumping, this solution however requires a provision of energy which is not always easily available.